In response to the increased demand for portable information devices, such as mobile phones or Personal Digital Assistants (PDAs), the demand for micro-camera devices is also increasing.
At present, a micro-camera device is fabricated by mounting an image sensor on a Printed Circuit Board (PCB), attaching a holder thereon, and mounting a lens module on the holder. The lens module is fabricated by combining a single-piece optical lens with a stop, a spacer, a vignetting structure, a barrel, an infrared (IR) filter, and the like.
FIGS. 1 to 3 are schematic views showing the process of fabricating a wafer-scale array of lenses in the related art.
The lenses are the key part determining the optical performance of a camera device, and are generally formed on a wafer-sized glass substrate by a replication process.
The lens array can be obtained in a wafer size, and the pitch between the lenses is made the same as the pitch between the image sensors.
A lens material 113 is applied onto a glass substrate 111, which is prepared on a wafer-scale, molds 112, each of which has a lens cavity array, are aligned with the glass substrate 111 using alignment marks 114, and then a wafer-scale lens array 110 is produced through a replication process.
Such structure makes it impossible to design a lens that is thinner than the thickness of the glass substrate 111. In order to overcome this limitation, a method in which, for example, trenches are formed on the glass substrate 111 has been proposed. However, this has the drawback of increasing the costs of processing the substrate.
Meanwhile, the process of assembling the lens module requires strict alignment with a small tolerance, which causes the costs of manufacturing the camera device to increase. In addition, ensuring the minimum alignment tolerance required for the assembly process acts as a limitation, which makes it difficult to design an ultra-thin camera device.
In addition, the process of assembling the lens module requires an increased number of parts, since a spacer is required in each step, and an opaque layer, which acts as a stop and a vignetting structure, is required. This increases the number of processes and the overall thickness of the camera device. The opaque layer, which acts as the stop and the vignetting structure, can be formed through a deposition process. However, this also requires an additional coating process.
In addition, in the finished camera device, the glass substrate and the lens material are exposed outwards at the side thereof, and the exposed transparent layer can allow external light to enter and be incident onto an image sensor. Accordingly, an additional coating process or a process of bonding an additional attachment to block the external light is required.